Chemistry - GOC Question with Solution | TestHub

The conjugate bases are $\mathrm{C}{\mathrm{H}}_3^{-}$, $\mathrm{O}{\mathrm{H}}^{-}$, $\mathrm{H}{\mathrm{S}}^{-}$ and $\mathrm{N}{\mathrm{H}}_2^{-}$. $\mathrm{C}{\mathrm{H}}_3^{-}$ and $\mathrm{N}{\mathrm{H}}_2^{-}$ and $\mathrm{O}{\mathrm{H}}^{-}$ sit in the same period, so electronegativity gives $\mathrm{C}{\mathrm{H}}_3^{-}$ $<$ $\mathrm{N}{\mathrm{H}}_2^{-}$ $<$ $\mathrm{O}{\mathrm{H}}^{-}$ in stability (weakest to strongest base reversed) : $\mathrm{C}{\mathrm{H}}_4$ $<$ $\mathrm{N}{\mathrm{H}}_3$ $<$ ${\mathrm{H}}_2\mathrm{O}$. $\mathrm{H}{\mathrm{S}}^{-}$ is larger than $\mathrm{O}{\mathrm{H}}^{-}$ and stabilises the charge better, so ${\mathrm{H}}_2\mathrm{S}$ is the strongest acid. Order : $\mathrm{C}{\mathrm{H}}_4(1)$ $<$ $\mathrm{N}{\mathrm{H}}_3(2)$ $<$ ${\mathrm{H}}_2\mathrm{O}(3)$ $<$ ${\mathrm{H}}_2\mathrm{S}(4)$.